• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.137-143
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• 2017

In the present study, Ni and $TaF_5$ were chosen as additives to enhance the hydriding and dehydriding rates of Mg. A sample with a composition of 80 wt% Mg + 14 wt% Ni + 6 wt% $TaF_5$ (named $80Mg+14Ni+6TaF_5$) was prepared by high-energy ball milling in hydrogen. Its hydriding and dehydriding properties were then examined. At the fourth cycle, the activated sample absorbed 3.88 wt% H for 2.5 min, 4.74 wt% H for 5 min, and 5.75 wt% H for 60 min at 593 K under 12 bar $H_2$. $80Mg+14Ni+6TaF_5$ had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of about 5.8 wt%. The sample desorbed 1.42 wt% H for 5 min, 3.42 wt% H for 15 min, and 5.09 wt% H for 60 min at 593 K under 1.0 bar $H_2$. Line scanning results by EDS for $80Mg+14Ni+6TaF_5$ before and after cycling showed that the peaks of Ta and F appeared at different positions, indicating that the $TaF_5$ in $80Mg+14Ni+6TaF_5$ was decomposed.

• 한국재료학회지
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• 제23권10호
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• pp.562-567
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• 2013

A 90 wt% Mg-10 wt% $NbF_5$ sample was prepared by mechanical milling under $H_2$ (reactive mechanical grinding). Its hydriding and dehydriding properties were then examined. Activation of the 90 wt% Mg-10 wt% $NbF_5$ sample was not required. At n=1, the sample absorbed 3.11 wt% H for 2.5 min, 3.55 wt% H for 5 min, 3.86 wt% H for 10 min, and 4.23 wt% H for 30 min at 593K under 12 bar $H_2$. At n=1, the sample desorbed 0.17 wt% H for 5 min, 0.74 wt% H for 10 min, 2.03 wt% H for 30 min, and 2.81 wt% H for 60 min at 593K under 1.0 bar $H_2$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ after reactive mechanical grinding showed Mg, ${\beta}-MgH_2$ and small amounts of ${\gamma}-MgH_2$, $NbH_2$, $MgF_2$ and $NbF_3$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ dehydrided at n=3 revealed Mg, ${\beta}-MgH_2$, a small amount of MgO and very small amounts of $MgH_2$ and $NbH_2$. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial hydriding rate and a larger quantity of hydrogen absorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$, which were reported to have quite high hydriding rates and/or dehydriding rates. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial dehydriding rate (after an incubation period) and a larger quantity of hydrogen desorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$.

• Journal of Periodontal and Implant Science
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• 제38권1호
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• pp.51-58
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• 2008

Purpose: In dental clinical fields, various periodontal membranes are currently used for periodontal regeneration. The periodontal membranes are categorized into two basic types: resorbable and non-resorbable. According to the case, clinician select which membrane is used. Comparing different membranes that are generally used in clinic is meaningful. For this purpose, this study evaluates histological effects of various membranes in canine one wall intrabony defect models and it suggest a valuation basis about study model. Material and Method: The membranes were non-resorbable TefGen $Plus^{(R)}$, resorbable Gore Resolut $XT^{(R)}$ and resorbable $Osteoguide^{(R)}$. One wall intrabony defects were surgically created at the second and the mesial aspect of the fourth mandibular premolars in either right or left jaw quadrants in two dogs. The animals were euthanized 8 weeks post-surgery when block sections of the defect sites were collected and prepared for histological evaluation. Results: 1. While infiltration of inflammatory cells were observed in control, TefGen $Plus^{(R)}$ and Gore Resolut $XT^{(R)}$, it was not observed in $Osteoguide^{(R)}$. 2. TefGen $Plus^{(R)}$ had higher integrity than others and $Osteoguide^{(R)}$ was absorbed with folding shape. Gore Resolut $XT^{(R)}$ was divided everal parts during resorbtion and it was also absorbed from inside. 3. Quantity of new bone and new cementum was not abundant in all membranes. 4. For histologic evaluation of membranes we should consider infiltration of inflammatory, migration of junctional epithelium, integrity of membrane, quantity of new bone and new cementum, connective tissue formation and aspect of resorption. Conclusion: This histologic evaluation suggests that $Osteoguide^{(R)}$ provides periodontal regenerative environment with less inflammatory state. It is meangful that this study model suggests a valuation basis about other study model.

• 한국토양비료학회지
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• 제5권1호
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• pp.1-8
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• 1972

수도재배(水稻栽倍)에 있어서 용성인비중(熔成燐肥中)에 함유(含有)된 규산(珪酸)의 효과를 기대(期待)하기 위하여서는 현행(現行) 용성인비(熔成燐肥)는 인산(燐酸)의 함량(含量)이 높으므로 다량시비(多量施肥)를 할경우 인산(燐酸)의 과용(過用)이 문제(問題)시되므로 인산함량(燐酸含量)이 낮고 규산함량(珪酸含量)이 많은 인산저농도(燐酸低濃度) 용성인비(熔成燐肥)를 제조(製造)하여 규산(珪酸) 및 인산(燐酸)의 효과를 기대(期待)코저 시험(試驗)하여 다음의 결과(結果)를 얻었다. 1. 고온로(高溫爐)에서 인광석(燐鑛石)을 주원료(主原料)로 하여 용융(熔融)한 결과(結果) 인산함량(燐酸含量)이 9.9%(구용율(枸溶率) 97%)이며 가용성(可溶性) 규산함량(珪酸含量)이 33%인 인산저농도(燐酸低濃度)의 용성인비(熔成燐肥)를 제조(製造)했다. 2. 정조중(精租重)은 시비수준(詩肥水準)에 따라 고도(高度)의 유의성(有意性)이 있었으며 300kg/10a구(區)에서 수량(收量)이 가장 높았다. 3. 인산저농도(燐酸低濃度)의 용성인비(熔成燐肥)를 이용(施用)하므로서 수도(水稻)의 수량구성요인(收量構成要因)중 수당입수(穗當粒數), 임실율(稔實率) 및 천입량(千粒量)이 증가(增加)되었다. 4. 생육기간중(生育期間中) 인산(燐酸)의 흡수량(吸收量)은 초기(初期)에서는 대조구(對照區)와 소량시비구(少量施肥區)가 많았으나 수확기(收穫期)에는 300kg/10a구(區)가 흡수량(吸收量)이 가장 컸고 500kg/10a 구(區)에는 억제(抑制)되는 경향(傾向)이었다. 규산(珪酸)의 흡수량(吸收量)은 인산(燐酸)과 같이 생육기간(生育初期)에는 소량시비구(少量施肥區) 흡수량(吸收量)이 높았으나 유수형성이후(幼穗形成以後) 수확기(收穫期)동안은 300kg/10a 구(區)까지 흡수량(吸收量)이 급격(急激)히 증가(增加)되었고 50kg/10a구(區)는 300/10a 구(區)와 비슷하였다. 5. 시험후(試驗後) 토양(土壤)중의 가용성배합량(可溶性酸含量)은 시비수준(施肥水準)에 따라 증가(增加)하였으며 기타 양(陽)이온도 같은 경향이었으나 인산(燐酸)은 100kg/10a 구(區)가 약간 낮았고 다른 구(區)는 대조구(對照區)와 비슷하였다. 6. 인산저농도(燐酸低濃度) 용성인비(熔成燐肥)의 이용(施用)으로 규산(珪酸)과 인산(燐酸)의 효과를 공(共)히 기대(期待)할 수 있으나 시험후토양(試驗後土壤)의 인산함량(燐酸含量)이 많이 잔류(殘有)되어 있으므로 인산농도(燐酸濃度)를 더 낮추어야할 필요성(必要性)이 있다.

• Journal of Welding and Joining
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• 제16권4호
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• pp.55-62
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• 1998

While excellent joint quality has been obtained using dry chamber underwater welding methods, the size limitations imposed by this process restrict its use for underwater construction work. The wet underwater shielded metal-arc welding eliminates this restriction but suffers from poor weld properties by the 1-pass bead-on-plate welding due to the excessive diffusible hydrogen. On the other hand, in the wet underwater welding, it is well known that the quantity of diffusible hydrogen in multi-pass welded parts reduce to less than that in 1-pass welded parts. Therefore, in this paper, welding experiments are made the 3-pass bead-on-plate welds by using TMCP and normalized steel plates and E4301 and cellulose coated electrode. After that, The amounts of the hydrogen absorbed into the 3-pass welded area were measured according to the JIS Z 3118 specification. The microstructural changes as well as the microhardness distribution after the underwater 3-pass welding were also investigated using Vickers microhardness tester and S.E.M and O.M. The results indicated that the quantity of diffusible hydrogen in 3-pass welded areas was reduced little less than a half of one of that in 1-pass welded areas at the specific welding condition. As a result, the cold cracking of 3-pass welded areas decreased by reduced effect of diffusible hydrogen. In the underwater 3-pass welding, the micrography of cold cracking fracture surface showed mainly the cleavage of hydrogen embrittlement.

• Journal of Ceramic Processing Research
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• 제20권6호
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• pp.609-616
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• 2019

The optimum powder to ball ratio was examined, which is one of the important conditions in reactive mechanical grinding processing. Yttria (Y2O3)-stabilized zirconia (ZrO2) (YSZ), Ni, and graphene were chosen as additives to enhance the hydriding and dehydriding rates of Mg. Samples with a composition of 92.5 wt% Mg + 2.5 wt% YSZ + 2.5 wt% Ni + 2.5 wt% graphene (designated as Mg-2.5YSZ-2.5Ni-2.5graphene) were prepared by grinding in hydrogen atmosphere. Mg-2.5YSZ-2.5Ni-2.5graphene had a high effective hydrogen-storage capacity of almost 7 wt% (6.85 wt%) at 623 K in 12 bar H2 at the second cycle (n = 2). Mg-2.5YSZ-2.5Ni-2.5graphene contained Mg2Ni phase after hydriding-dehydriding cycling. Mg-2.5YSZ-2.5Ni-2.5graphene had a larger quantity of hydrogen absorbed for 60 min, Ha (60 min), than Mg-2.5Ni-2.5graphene and Mg-2.5graphene. The addition of YSZ also increased the initial dehydriding rate and the quantity of hydrogen released for 60 min, Hd (60 min), compared with those of Mg-2.5Ni-2.5graphene. Y2O3-stabilized ZrO2, Ni, and graphene-added Mg had a higher initial hydriding rate and a larger Ha (60 min) than Fe2O3, MnO, or Ni and Fe2O3-added Mg at n = 1.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1991-1999
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• 2021

The response changes of the specific growth rate of Lemna minor duckweed was modeled using the logarithms of frond numbers on tritium activity concentration and gamma radiation dose from cobalt 60. The concept of average specific growth rate depends on the general exponential growth pattern, where toxicity is estimated based on the effect on the growth rate. One of the main questions of the effect of the radiation dose on duckweed is how to correlate the effect of beta radiation with the effect of any other radiation for modeling radiation on Lemna minor. Experimental data were extrapolated by utilizing the OECD guidelines. A linear relationship of absorbed dose and activity concentration was obtained for the average dependency growth rate of Lemna minor as D = (0.1257)·A^0.585. The dose rate of gamma irradiation from ⁶⁰Co increases with tritium activity dependence, on the specific growth rate of the Lemna minor duckweed. An increase in the tritium activity causes a decrease in the specific growth rate of the Lemna minor duckweed. It indicates that as the quantity of the beta radiation dose increase in Lemna minor duckweed, a higher quantity of gamma radiation will be required to cause the same effect in the specific growth rate of Lemna minor duckweed. The relation between the inhibition of the Lemna minor seedling growth and gamma and beta radiation dosage agrees roughly with that between the decrease of survival rate or fertility and dosage.

• 한국방재학회 논문집
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• 제9권4호
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• pp.11-20
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• 2009

천연골재 고갈과 환경파괴문제 해결을 위한 방안과 경량콘크리트의 구조물 적용 실용화를 위해 폐기물 활용 인공경량골재를 이용하여 경량콘크리트를 제조하고, 물-결합재비에 따른 기본 물성을 평가하였다. 연구과 경량골재의 사전 흡수수 관리를 위한 방안을 제시하였으며, 굳지 않은 콘크리트의 특성은 경량골재를 사전 흡수하여 적용할 경우 물-결합재비에 관계없이 일반콘크리트와 유사한 방법으로 제어할 수 있는 것으로 나타났다. 경량콘크리트의 경화 후 단위용적질량은 물-결합재비, 건조 조건, 철근고려에 따라 1,668${\sim}$1,998 $kg/m^3$의 범위로서 일반콘크리트에 비해 14.6${\sim}$21.0% 의 감소를 나타내었다. 경량골재 사전 흡수수는 물-결합재비에 따라 상이한 증발수량을 나타내었으며, 물-결합재비가 낮을수록 노건조 증발수가 커져 내부양생수로서의 역할 가능성이 증가할 것으로 생각된다. 동일 물-시멘트비에서 경량콘크리트는 일반콘크리트에 비하여 골재의 강도차이로 인해 낮은 강도를 나타내며, 기건 양생 시 일반콘크리트의 경우 물-시멘트비 0.3은 물-시멘트비 0.4, 0.5에 비해 강도 증진 효과가 감소하지만, 경량콘크리트의 경우 물-결합재비가 낮을수록 강도 증진 효과가 증가하는 것으로 나타났다.

• Applied Biological Chemistry
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• 제14권3호
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• pp.183-189
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• 1971

규산재료(珪酸材料)인 강사(江砂) 및 석영(石英)과 농용(農用) 소석회(消石灰)의 혼합(混合) 용융물(溶融物)에 대(對)한 규산질(珪酸質) 비료(肥料)로써의 효과(效果)를 구명(究明)코져 유효규산함량(有效珪酸含量)이 낮은 답토괴(畓土壞)에서 수도(水稻)에 대(對)해서 천연(天然) 규회석(珪灰石)을 대조(對照)로 시비처리(施肥處理)하여 시험(試驗)한 결과(結果) 1. 모래용융물(溶融物)이 석영용융물(石英溶融物)에 비(比)하여 N/2 염산가용규산함량(鹽酸可溶珪酸含量)이 높고 2% 구연산 가용규산함량(可溶珪酸含量)은 석영용융물(石英溶融物)이 모래용융물(溶融物)보다 높았다. 2. 벼의 규산흡수량(珪酸吸收量)은 석영용융물(石英溶融物)에서 가장 크고 모래용융물(溶融物)과 규회석(珪灰石)은 거의 같았으며 이용율(利用率)은 천연(天然) 규회석(珪灰石)이 가장 높고 석영용융물구(石英溶融物區)가 모래용융물구(溶融物區)보다 높았다. 3. 정조수량(正租收量)은 규산물질(珪酸物質)의 시용(施用)으로 수량구성요소중(收量構成要素中) 수당입수(穗當粒數), 등숙률(登熟率) 및 천입중(千粒重)의 증가(增加)로 증수(增收)되었으며 공시재료중(供試材料中) 석영용융구(石英溶融區)에서 가장 크게 증수(增收)하였으며 대조구(對照區)${\fallingdotseq}$모래용융물(溶融物) 100kg/10a<천연규회석(天然珪灰石)${\fallingdotseq}$모래용융물(溶融物) 300kg/10a${\fallingdotseq}$석영용융물(石英溶融物) 100kg/10a<모래용융물(溶融物) 500kg/10a${\fallingdotseq}$석영용융물(石英溶融物) 300kg/10a<석영용융물(石英溶融物) 500kg/10a의 순서(順序)이었다.

• 대한기계학회논문집B
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• 제24권1호
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• pp.29-38
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• 2000

It is observed that the cooling capacity of impinging water jet is affected by the seasonal conditions in steel manufacturing process with large scale. To confirm this phenomena, the cooling experiments of a hot steel plate by a laminar jet were conducted for two different initial ambient air temperature($10^{\circ}C$ and $40^{\circ}C$) in a closed chamber, and an inverse heat conduction method is applied for the quantitative comparison. It is found that the cooling capacity under $10^{\circ}C$ air temperature is lower than that under $40^{\circ}C$, as is the saturated water vapor is more easily observed, and the amount of total extracted heat in the case of $10^{\circ}C$ is smaller by nearly 15% than that of $40^{\circ}C$ case. From these results, it is thought that the quantity of water vapor, which could be absorbed until saturation, effects on the mechanism of boiling heat transfer.